The brains of Black adults in the U.S. age more quickly than those of white and Hispanic adults, showing features linked to Alzheimer’s disease and other dementias as early as mid-life, according to a new study.

The study, published Monday in JAMA Neurology, analyzed the MRI scans of nearly 1,500 participants from two racially and ethnically diverse cohorts. It found that Black adults in mid-life — on average, in their mid-50s — were more likely than white or Hispanic adults of the same age to have a higher prevalence of white matter lesions, markers of cerebrovascular disease that are associated with cognitive decline and Alzheimer’s disease.

Previous research has established stark racial disparities in Alzheimer’s disease, which affects more than 6 million Americans. Hispanic people are 1.5 times more likely to have the disease than white people, while Black people are twice as likely to have the disease compared to those who are white. The new study strengthens the case that vascular disease may be especially detrimental to brain health in Black populations, and may start to affect the brain far earlier in life than previously thought.